1. Field of the Invention
The present invention relates to communication networks, and more specifically to a method and apparatus implemented for supporting multiple point-to-point sessions between network devices on an Asynchronous Transfer Mode (ATM) backbone.
2. Related Art
Point-to-point sessions (“PPP sessions”) are often set up between remote systems (e.g., personal computer systems at homes) and communication networks. A PPP session generally allows data transfer between a remote system and a termination device situated at the edge of a communication network. Point-to-point protocol (PPP) described in request for comment (RFC) 1661, available from www.ietf.org, is a common protocol using which point-to-point sessions are established.
The termination device usually provides additional communication to enable a remote system (at one end of a session) to communicate with a target host as is also well known in the relevant arts. The communication between a host and a remote system forms the basis for several user applications. As the host systems and remote systems are at either end of corresponding applications, the two systems are commonly referred to as end systems.
Asynchronous Transfer Mode (ATM) is often used to provide high speed backbone in communication networks. As is well known, virtual circuits are provisioned in the ATM backbone between network devices. A network device refers to a device which performs the switching task in forwarding ATM cells. Virtual circuits provide the basis for transfer of data in ATM backbone. Supporting PPP sessions on ATM backbone also thus requires provisioning of virtual circuits.
Each virtual circuit generally consumes several resources on intermediate network devices in the path of a virtual circuit. Typical resources consumed include memory space, queue structures, etc., either in software or in the application specific integrated circuits (ASIC) supporting the data transfers on the virtual circuits. Optimal use of such resources is important to provide superior services (high throughput, low latency, etc.) to the end applications as is well known in the relevant arts.
In one prior approach based on AAL5 (ATM Adaptation Layer 5), a virtual circuit is provisioned for each point-to-point session. Unfortunately, the resulting large number of circuits may consume an undesirable amount of resources on the intermediate network devices, and the solution may thus be not suited in several environments.
In another approach based on tunnels, a tunnel may be set up using one virtual circuit and several sessions may be supported on the single virtual circuit. An implementation of tunnel is described in RFC 2661, which is incorporated in its entirety herewith. Such a solution minimizes the resources consumed from intermediate devices. However, the solution requires additional fields within the payload of the ATM cell, with the result that the effective data (for user applications) throughput can be proportionately reduced.
Accordingly what is needed is a method and apparatus which enables many point-to-point sessions to be supported on an ATM network while minimizing the overhead on intermediate devices and yet potentially allowing for a high effective data throughput for end applications.